Self contained igniter-burner and process



p 25, 1952 R. c. PRYOR ETAL 3,055,427

SELF CONTAINED IGNITER-BURNER AND PROCESS Filed July 13, 1959 INVENTORSR.C. PRYOR R.J. BENNETT I BYl A T TORNEYS United States Patent Oiilice3,055,427 Patented Sept. 25, 1962 3,055,427 SELF C(BNTAINED IGNITER-BURNER AND PROCESS Robert C. Pryor and Richard J. Bennett, Bartlesville,

@irim, assignors to Philiips Petroleum Company, a corporation ofDelaware Filed July 13, 1959, Ser. No. 826,504 Claims. (Cl. 166-39) Thisinvention relates to a self-containing-igniter burner for igniting acombustible fuel pack in a borehole adjacent a carbonaceous stratum andto a process for igniting such a fuel pack and igniting the stratum.

In situ combustion in the recovery of hydrocarbons from undergroundstrata containing carbonaceous material is becoming more prevalent inthe petroleum industry. In this technique of production, combustion isinitiated in the carbonaceous stratum and the resulting combustion zoneis caused to move thru the stratum by either inverse or direct air drivewhereby the heat of combustion of a substantial proportion of thehydrocarbon in the stratum drives out and usually upgrades a substantialproportion of the unburned hydrocarbon material.

The ignition of carbonaceous material in a stratum around a boreholetherein followed by injection of air thru the ignition borehole andrecovery of product hydrocarbons and combustion gas thru anotherborehole in the stratum is a direct air drive process for effecting insitu combustion and recovery of hydrocarbons from the stratum. In thistype of operation the stratum usually plugs in front of the combustionzone because a heavy viscous liquid bank of hydrocarbon collects in thestratum in advance of the combustion zone which prevents movement of airto the combustion process. To overcome this difiiculty and to permit thecontinued progress of the combustion zone thru the stratum, inverse airinjection has been resorted to. By this technique, a combustion zone isestablished around an ignition borehole by any suitable means and air isfed thru the stratum to the combustion zone from one or more surroundingboreholes.

In situ combustion techniques are being applied to tar sands, shale,Athabasca sand and other strata in virgin state, to coal veins byfracturing, and to strata partially depleted by primary and evensecondary and tertiary recovery methods.

One of the basic methods of igniting a carbonaceous stratum preparatoryto producing the same by in situ combustion comprises burning a solidparticulate fuel pack in a well adjacent the stratum to be ignited and,when surrounding stratum has been raised to ignition temperature,passing air or other oxygen-containing, combustionsupporting gas(diluted or enriched air) into the hot stratum so as to ignite the same.

(Dharcoal in the form of briquettes or other small pieces, alone, or inadmixture with ceramic pieces such as pebbles, broken fire brick, etc.,and porous ceramic pieces such as alumina pebbles soaked with heavy oil,have been successfully utilized as a fuel pack for igniting a stratum.In shallow strata, the charcoal has been successfully ignited bydropping onto the top of the charcoal pack a mass of ignited charcoal oran ignited railroad fuse and injecting combustion-supporting gas intothe charcoal pack.

The problem of ignition of a fuel pack in a deep well is substantiallydifferent from that in a shallow well, since the gravitating ignitedmaterial falls thru a zone of little or no oxygen content and is rapidlycooled so that the material is not burning when it reaches the charcoalpack. This invention provides a method and device for igniting a fuelpack regardless of the depth of the stratum to be ignited.

Accordingly, the principal object of the invention is to provide a noveligniter and method for igniting a fuel pack in a well within acarbonaceous stratum. Another object is to provide an igniter-burner forigniting a combustible fuel pack which is self-contained and does notrequire fuel and air conduits extending from the well head to the fuelpack, and which is applicable to deep strata. A further object of theinvention is to provide an igniter-burner for igniting a stratum, whichis so compact that it can be lowered in the well thru conventional welltubing. It is also an object to provide a method of igniting andproducing a carbonaceous stratum by inverse air injection which does notrequire the reversal of air flow from direct to inverse injection afterigniting the stratum. Other objects of the invention will becomeapparent upon consideration of the accompanying disclosure.

The igniter-burner of the invention comprises a pair of cylindrical fueltanks of small diameter supported in axial alignment with each other andwith a combustion vessel and a burner nozzle, with a separate conduitconnecting each tank with the combustion chamber of the combustionvessel. The igniter-burner with one of its tanks filled with compressedoxygen and the other filled with compressed fuel gas is ignited at thesurface, the flame is adjusted for maximum operating efliciency, and theburner is lowered into the well containing the fuel pack on a wire orcable by a conventional Windlass or winch thru well tubing in instanceswhere the tubing is necessary for production, and thru the well casingwhere the tubing is not essential to production. When the burnercontacts the top of the fuel pack it is held in this position until ithas burned a suificient length of time to ignite a large section of thefuel pack. This may require anywhere from 10 or 15 minutes to an hour ortwo.

A more complete understanding of the invention may be had by referenceto the accompanying schematic drawing of which FIGURE 1 is an elevationin partial section of a preferred embodiment of the self-containedigniterburner of the invention, and FIGURE 2 is an elevation showing anarrangement of apparatus, including the burner of FIGURE 1, positionedin a borehole for igniting a carbonaceous stratum.

Referring to FIGURE 1, burner 10 comprises a cylindrical oxygen tank 12and a cylindrical fuel tank 14 connected by a conduit 16 of the samediameter as the tanks and welded to the tanks at each end by welds 18 soas to hold same in axial alignment. The ends of tanks 12 and 14 aregenerally hemispherical in order to withstand high pressures of theorder of 1000 or more pounds per square inch. A mixing vessel 20 havinga top closure 22 threaded into its upper end at 24 is held in axialalignment with the tanks by means of a conduit 26 similar to conduit 16welded to the lower tank by weld 28. Members 22 and 24 are of the samediameter as the internal diameter of conduit 26 and closure 24 is weldedthereto by weld 3t Mixing vessel 20 has an axial orifice 32 (which maybe in the form of a venturi) dividing the vessel into a. primary mixingchamber 34 and a larger storage and surge chamber 36. Flame arrester 38is threaded into the outlet end of the mixing vessel and is providedwith small holes or passageways 40 for injection of gas into nozzle orburner tip 42. Nozzle 42 is screwed into the outlet end of the mixingvessel against flame arrester 38 and is provided with annular shoulder44 which seats against seal ring 45. Seal ring 46 is provided betweenend closure 22 and vessel 20. The end of burner tip 42 is provided withmember 48 which contains a plurality of conduits or passageways 50 thruwhich the combustible mixture of fuel gas and oxygen is jetted forignition and burning below the tip.

A conduit 52 leads from oxygen tank 12 thru fuel tank 14 into primarymixing chamber 34 and is provided with an upper valve 54 and a lowervalve 56. A separate conduit 58 leads from fuel tank 14 thru closure 22into primary mixing chamber 34 and is provided with a control valve 60.An orifice 62 is positioned in the end of each of conduits 52 and 58 tocontrol the rate of flow of the oxygen and fuel into the mixing chamber.A valved fill line 64 and a similar valved fill line 66 are connectedwith tanks 12 and 14, respectively. Openings 67, 68, 69, and 70 in theirrespective conduits are provided for access to the valves and linesconnected with the tanks.

A tip guide and shield 72 forms an annulus 74 around burner tip 42,being of the same inner diameter as the outer diameter of mixing vessel20 and is welded thereto by weld 76. Shield 72 extends below the burnertip and is perforated by ports 78 to aid in the venting of hot gas andfiame from the tip of the burner. A threaded connector Silon the upperend of tank 12 permits attachment of a threaded ring connector or othercable attaching device (not shown) for lowering the igniterburner intothe well.

Referring to FIGURE 2, la combustible stratum 82 is penetrated by a well84 which is packed with a fuel pack 85, such as charcoal briquettes. Acasing 88 extends from the well head 89 to the approximate upper levelof stratum 82 land is cemented at 90. A tubing string 92 extends thruwell head 89 to a level just above the lower end of the casing andburner 10 is suspended in the tubing by means of cable 94 with its lowerend in the top of the fuel pack. Cable 94 is attached to winch orWindlass 96 and extends over pulley )8. A valved conduit provides forinjecting or venting gas into or from the casing.

Conventional well tubing is 2 /2 or 3 inches I.D., which means that theigniter-burner must have an external diameter of about 2% or 2% inchesto accommodate conventional tubing. Tanks v12 and 14 can be fabricatedin lengths up to 10 or 15 feet which provides ample supplies of oxygenand fuel, even though their diameters are small, since the oxygen andfuel gas can be compressed to pressures of the order of 1,000 lbs.p.s.i.g.

In operation, the burner with tanks filled with highly compressed gases(oxygen in one tank and acetylene, ethylene, ethane, propane, propylene,butane, butylene, or mixtures thereof, or any liquefied petroleum gas)is ignited by opening valves 54-, 56, and 60 and igniting the efiluentgas at burner tip 4-2. After adjusting the flame to optimum heatingefficiency, the burner is lowered by cable 94 to the position shown inFIGURE 2 and held in this position until a substantial upper section ofthe fuel pack is heated to ignition temperature. The hot fuel pack iscontacted at this time with oxygen by means of excess provided in thecombustion mixture of the mixture of the burner or by air injected intothe fuel pack thru line 100 and down the casing in instances where thedriving of hot gases into the stratum does not effect plugging. In mostinstances, it is more desirable to vent the combustion gases thin line100 and feed combustionsupporting gas to the hot fuel pack thru stratum82 by injecting air or other combustion-supporting was into the stratumthru a ring of offset injection wells surrounding ignition well 84. Inthis case an" passing thru the stratum into the fuel pack burns the fuelpack progressively from the top to the bottom thereof and, as theadjacent stratum is heated to combustion supporting temperature,ignition thereof is effected and the resulting combustion zone or frontautomatically moves radially thru the stratum toward the offset wells.

When simultaneously burning the fuel pack and initiating combustion ofthe stratum by injecting combustionsupporting gas thru the stratum tothe ignition well, it is essential to include in the injected gas a lowconcentration of fuel gas such as any of a mixture of the normallygaseous hydrocarbons. A concentration in the range of about 1 to 4volume percent of the fuel gas in the injected gas is effective inmoving the fire front into the stratum. After a substantial area of thestratum around the ignition well has been ignited, the injected of fuelgas into the stratum may be terminated, but continued injection of fuelgas with the injected air aids in the in situ combustion process byincreasing the rate of propagation of the combustion front and thepercentage of hydrocarbons recovered from the stratum.

While the oxygen tank llis shown in the upper position in the burnerwith the fuel tank in the lower position, the position of these tanksmay be reversed, of course. It is also feasible to operate the burnerwithout tip shield 72, but use of this shield protects the burner tipand its use is preferred.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

We claim:

1. A self-contained igniter-burner for igniting a combustible fuel packin a well comprising in combination, when positioned in uprightoperating position, a first vertically elongated pressure tank and asecond vertically elongated pressure tank rigidly attached one above theother in axial alignment for lowering into a well; a mixing vesselaxially aligned with and below said tanks; a transverse partition acrosssaid vessel having an axial orifice therein and dividing said vesselinto an upper small primary mixing zone and a lower larger secondarymixing and surge zone; a separate conduit connecting each tank with theupper end of said primary mixing chamber; a flow orifice in the end ofeach said conduit leading into said primary mixing chamber; a flamearrester across the lower open end of said secondary mixing zone; aterminal burner nozzle axially attached to the lower end of said mixingvessel adjacent said flame arrester, said burner nozzle having exhaustports open to said well; a burner nozzle shield surrounding the lowerend of said vessel, forming an annulus with said nozzle, and extendingbelow said nozzle; and ports in the lower end of said shield.

2. The burner of claim 1 adapted to pass thru a well tubing, said tanksbeing welded to opposite ends of an interconnecting conduit of anoutside diameter not exceeding the outside diameter of said tanks andsaid tanks having an outside diameter less than the inside diameter ofsaid tubing; said vessel comprising an upper end closure memberconnected to the lower end of the adjacent tank by means of asurrounding and engaging conduit of outside diameter not exceeding theoutside diameter of said tanks welded to the adjacent tank; and saidshield surrounding and engaging the lower end of said vessel.

3. A process for igniting a fuel pack in a well adjacent a combustiblestratum comprising positioning in said well adjacent the top said fuelpack a separate, stored supply of compressed oxygen and a separate,stored supply of compressed fluid fuel; injecting fuel and oxygen fromtheir respective separate supplies into a mixing zone adjacent said packto form a combustible mixture; ccmbusting said mixture and ejecting theresulting flame and hot gases onto said fuel pack until same is raisedto combustion temperature; and contacting said fuel pack with freeoxygen so as to ignite same.

4. The process of claim 3 wherein said free oxygen for igniting saidfuel pack is supplied in said combustible mixture.

5. The process of claim 3 wherein said free oxygen for igniting saidfuel pack is supplied by passing air thru said stratum from at least oneoffset well therein.

6. The process of claim 5 wherein said air is admixed with fuel gas in aconcentration in the range of about 1 to 4 volume percent.

7. The process of igniting a permeable carbonaceous stratum around anignition well therein which comprises effecting the steps of claim 5 andcontinuing the injection of air and fuel gas :thIll said stratum so asto consume sufiicient fuel pack to raise the temperature of said stratumadjacent said fiue1 pack to ignition temperature: further continuingsaid injection so as to ignite said stratum and move a resultingcombustion front into said stratum away from said ignition Well; andrecovering produced hydrocarbons rthru said ignition well.

8. The process of claim 3 wherein said fuel is propane.

9. The process of claim 3 wherein said fuel is acetylene.

10. The process of claim 3 wherein said gas is liquified petroleumgases.

References Cited in the file of this patent UNITED STATES PATENTSStickney Sept. 20, Napolit-an May 13, De Kaiser et a1. Oct. 7, De Kaiseret a1. Oct. 7, Stroebel May 11, Shannon et all Aug. 1 6, Lurie Aug. 14,Damm July 16, Mayes et a1. Feb. 23, M acLeod Jan. 24, Koch Dec. 31,Trarrtha-m et a1. June 9, De Priester July 21,

